Fast 802.11 link adaptation for real-time video streaming by cross-layer signaling

The quality of real-time video streaming over wireless links is significantly reduced due to packet losses and delays caused by rapid changes of the link conditions. We resolve this problem by two solutions. First, we have developed a responsive MAC adaptation method using SNR and packet loss statistics. The second solution depends on the first one; it allows the MAC to communicate information about changes of link conditions to the video codec. Together, these solutions prevent packet losses and skipped frames, both of which have an adverse effect on the visual quality of the decoded video. We present the results of a streaming video experiment using an 802.11a link between a fixed and a mobile station. We show that, with the cross-layer signaling between the MAC-layer and the video coder, a 4 dB increase of visual quality is achievable.